With thriving Internet of Things (IoT), the conventional earphone field has also changed, and in addition to a play function, intelligence characteristics of an information exchange such as a heart rate detection, a step recording and the like are gradually added.
At present, it is known a wired earphone that can perform a communication transmission via an audio signal path corresponding to a host side and an earphone interface. A main communication procedure is as follows: (1) a terminal device encodes and modulates data that needs to be transmitted to an earphone; (2) the terminal device performs a digital-to-analog conversion on a modulated signal; (3) the terminal device transmits the modulated signal after the digital-to-analog conversion to the earphone through a left channel line or a right channel line of an earphone cable connected to the earphone interface; and (4) the earphone demodulates and decodes a received signal. In this procedure, on the one hand, a signal is transmitted by a channel line (for example, the left channel line or the right channel line), and it is necessary to recover a carrier by a carrier recovering module at the receiving end, to perform a signal demodulation. A conventional carrier recovery usually employs a phase-locked loop circuit and the like; on the other hand, it is also necessary to decode the signal through a digital circuit. Therefore, a digital circuit structure used for demodulating and decoding is more complex and the cost is also higher.